Experiment 3: Identification of an Unknown Mixture by Extraction, Recrystallization, and Melting Point Determination Name: Shahrukh Alvi Partner: Emad El-Masri Student ID: 104030390 GA: Terrence Yep, Michael Stanesic Section: 56 Abstract In this experiment a two base liquid‐liquid extraction technique was used to separate and isolate two components of an unknown mixture. In this process, acid-base reactions were used based on the difference in the solubility of a compound between two immiscible liquids1. After the unknown compounds were extracted, isolated, and recrystallized they were identified by their melting point. These were then matched with a list of compounds given; with their solubilities and melting point …show more content…
Carboxylic acids, contain the carboxyl group (‐COOH), and are the most acidic simple organic compounds; allowing them to readily donate protons. Phenols (contain OH-), however, are weak organic acids, and therefore do not donate protons as readily making them more difficult to deprotonate. To separate the unknown mixture the proper bases are to be used in the correct order to pull out one of the possible products into an aqueous state. Sodium bicarbonate is therefore used to deprotonate carboxylic acids, since it is not strong enough to deprotonate the phenol since it has a stronger hold onto its H+ ion. The carboxylic acid separates and deprotonates when the unknown mixture is mixed with sodium bicarbonate, forming an aqueous layer which now consists of the carboxylate anion; ready to be extracted. This is repeated around 4 times to ensure all the carboxylic acid, if any, is separated and removed into a beaker. This leaves an organic layer still remaining which should contain phenol or a neutral compound. To find out NaOH is now mixed into the remaining mixture, which is a stronger base, and is therefore able deprotonate the phenol better because phenol holds on to its protons more tightly than the carboxylic acid. This again forms an aqueous layer, which is immiscible with yet another organic …show more content…
The literature melting point range that 2-chlorobenzoic acid is supposed to be found in is 138°C-140°C9. Therefore the melting point value that was found for 2-chlorobenzoic acid compared to the expected range is quite close with marginal error. The literature melting point range for triphenylamine is supposed to be 124°C-128°C9. This is also very close to the value of 127.8°C that was obtained in the experiment. The value that was found corresponds to triphenylamine, as it falls right within its melting point range. Since no compounds were extracted after NaOH was put in, the remaining organic product would have to be a neutral compound. Therefore, the rotovap and the gravity filtration processes were used to obtain a purified product. After, this was done and a precipitate was formed it could be concluded that the product must be a neutral compound. Finally after observing the melting point it could be further deduced that the compound was indeed triphenylamine as the melting corresponded to its melting range. An error that could have occurred regarding the extraction of the organic compound may have been that there might have been impurities that could have been mixed with the compound that was extracted; but these would most likely be negligible since the compounds melting point still landed within the range. For the melting point of 2-chlorobenzoic acid, it was very